I work at a electric arc furnace. We measure a lot of items on our furnace and found that some weeks we preform well and other we do not (kwh/ton). With everything else being equal i believe that the utility's available short circuit current is affecting this. The utility feeds our substation 161kv + or - 7%. This is fed into a 50MVA 161kv to 13.8kv transformer. This 13.8kv is then distributed to our 45 mva arc furnace transformer that goes from 13.8kv to 500-800V. My question is, is there a way to calculate the available short circuit current on a system with only knowing my transformers and the incoming voltage. The 161kv line jumps 2-3kv when we arc our furnace. I figure this fluctuation in the 161kv line while running would give some indication on how stable their line is.